Circuit boards and the IC substrates produced for the optoelectronics and semiconductor industries are trending toward high-speed, high density, being intensive, and high integration because rise of “Cloud”, “Internet” and “Internet of things”, enhancements of 4G and 5G communication technologies, and improvement of display technologies. The required properties of the circuit boards and the IC substrates of the future are not only low dielectric constant and high insulation, but also low dielectric loss and high thermal conductivity. Moreover, they should be designed for heat dissipation of different applications, e.g. controlling the direction and distribution of their high thermal conductive path. For example, the copper foil substrate in a circuit board is concisely represented as copper foil/dielectric layer/copper foil, and the middle dielectric layer is usually composed of resin, glass fiber cloth, or insulation paper with low thermal conductivity. Therefore, the copper foil substrate has a poor thermal conductivity along its thickness direction. Enhancing the thermal conductivity of the middle dielectric layer may dramatically improve the thermal conductivity along its thickness direction. One conventional method adds a thermally conductive material into the dielectric layer. The thermally conductive material is usually randomly arranged, so that a large amount of the thermally conductive material should be added for increasing the thermal conductivity of the dielectric layer. However, too much thermally conductive material (filler) will dramatically increase the dielectric constant of the dielectric layer and the related cost. Another way is to magnetically align a high thermal conductive material along a specific direction (e.g. the thickness direction of the dielectric layer), thereby achieving a high thermal conductivity along a specific direction. However, the thermally conductive material should be inherently magnetic. A non-magnetic and thermally conductive material needs a magnetic field of high intensity (or a long magnetic alignment period) to be aligned.
Accordingly, a magnetic, insulative, low dielectric loss, and thermally conductive material is called for a dielectric layer with high thermal conductivity, insulation, and low dielectric loss.